Their population at one site, the Yellingbo Nature Conservation Reserve, has declined by more than 60 per cent over the past decade and now numbers just 40 individuals, says Dan Harley at Zoos Victoria in Melbourne. “Severe deterioration in habitat conditions has driven the decline.”

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Knowing how many possums are left is crucial to determining if conservation measures are working, he says. Checking the nest boxes supplied for the possums to live in isn’t enough. If they’re not in, it is hard to know if the family has moved to a new nest, left the area – or worse. So, Harley tried using the possum chattering call. He found they often approach and reply (Australian Mammalogy, doi.org/4rx).

The technique isn’t perfect, says Harley, but it could complement other counting methods. There are false negatives&colon; 31 per cent of his calls didn’t elicit responses, despite him seeing a possum nearby.

This article appeared in print under the headline “Chat to possums to save them”